Geology Through Literature:
Hans Christian Andersen's: The Comet (1869)
The Comet (1869)
Now there came a comet with its shiny nucleus and its menacing tail. People from the great castles and people from the poor huts gazed at it....
But a little boy and his mother still stayed inside their room. The mother believed ... that her son would soon die. The little boy lived many more years on earth. Indeed he lived to see the comet return sixty years later.
"This is the time to look at the comet," cried their neighbors....
The boy saw the bright ball of fire, with its shining tail. Some said it was three yards long, while others insisted it was several million yards long—such a difference.
In general a comet is is a body of ice, rock, and organic compounds that can be up to several miles in diameter. "Comets are thought to originate from a region beyond the orbits of the outermost planets. Scientists believe that gravitational perturbations periodically jar comets out of this population, setting these "dirty snowballs" on orbital courses that bring them closer to the Sun. Some, called long-period comets, are in elliptical orbits of the Sun that take them far out beyond the planets and back. Others, called short-period comets, travel in shorter orbits nearer the Sun" (Nasa.gov).
|Comet 153P/Ikeya-Zhang which has the longest known tail at over a billion kilometers. Image courtesy of NewScientist.|
Although many comets are known to have a return period, much of the comets with known return periods had only been discovered fairly recently. There are two types of comets based on their orbital periods; known as long-period comets, which are comets with orbital periods greater than 200 years, and short-period comets, with orbital periods less than 200 years. Even the short-period comets can be broken up into Halley-Type comets, which have orbital periods between 20 and 200 years, and Jupiter-family comets, that have orbital periods less than 20 years.
|The Great Comet of 1861 as painted by E. Weiss. Image courtesy of Wikipedia.|